1. Technical Field of the Invention
The present invention relates to an improved spring latch lock.
2. Prior Art
It is well known that spring latch locks are devices to close and open doors, main entrances, gates and the like, generally comprising a box body with a front plate and a sliding latch actuated by a handle.
Inside the box body there are the actuating mechanisms for the spring latch that can be reached and operated from outside through a handle which is inserted in a corresponding hole made on one or both sides of the box body. The locks are arranged hidden inside a corresponding housing made in the thickness of the door, entrance or gate, the actuating handle of the latch protruding from at least one side thereof.
Reliability of operation of the above mentioned locks is generally recognised as well as their functional limits with regard to the different applications for which said locks may be intended.
A first recognised limitation is the constructional form of the latch having a fixed length so that its portion protruding from the faceplate cannot be modified.
This involves that the same lock cannot be used for different applications, when each application requires a different protrusion of the latch from the corresponding faceplate.
Thus, for instance, the same lock cannot be indifferently applied to a door, a main entrance or a gate having different penetrations of the latch in the frame. The same happens for instance in rooms provided with doors identical to each other to which however different penetrations of the latch in the frame should be carried out whereby it is necessary to use locks with the same box body but having different performances with different latch protrusion.
Moreover identical locks but having different latch protrusions are not interchangeable.
In order to make easier closure of the door, main entrance or gate to which the lock is applied the protruding end of the latch has a bevel that during the closing operation is forced against the frame promoting the elastic return of the latch inside the box body.
When the closing operation is ended, the latch comes out automatically from the box body and is inserted into the rabbet of the frame.
This involves the further drawback that the same lock cannot be applied indifferently to door, entrances or gates having either right hand or left hand closures so that a lock provided with a right hand bevelled latch cannot be applied to doors with left hand closure and viceversa.
In order to overcome the above mentioned limitations, locks are made provided with adjusting means allowing to change the length of the latch protruding portion and to rotate the latch so that the bevel is always facing the frame irrespective of the fact that the lock is applied to a door, entrance or gate having either a right hand or left hand closure.
These locks, however, have the drawback that said adjustments are difficult to be carried out.
More particularly the locks having the possibility to change the orientation of the latch bevelled portion relative to the frame, show a greater constructional difficulty because the latch must be made in two coaxial parts that can be mutually blocked through screws, where the latch protruding portion can be turned relative to the part lodged inside the box body.
Another drawback consists in that, in order to change the latch protrusion, the lock must be taken out from its housing, the box body must be opened in order to act on the adjusting means to define the required protrusion of the latch.
After having carried out such an adjustment, the box body is again closed, the lock is again assembled and it is also necessary to check whether the length of the protruding portion meets the requirements.
If the length of the protruding portion is not satisfactory, the above mentioned operations should be repeated.
Therefore, it is clear that such an adjustment is a long and difficult operation. Moreover such an adjustment must be carried out by persons having at disposal proper tools and with specific professional skill.